Ionization vacuum gauge with x-ray and ultraviolet ray shielding



Aug. 26, 1969 J. GROSZKOWSKI IONIZATION VACUUM GAUGE WITH X-RAY AND ULTRAVIOLET 'RAY SHIELDING Filed May 17. 1967 Flq4 INVm

United States Patent 3,463,956 IONIZATION VACUUM GAUGE WITH X-RAY AND ULTRAVIOLET RAY SHIELDING Janusz Groszkowski, Nowowiejska 22/7, Warsaw, Poland Filed May 17, 1967, Ser. No. 639,102 Claims priority, application Poland, May 17, 1966, P 114,624 Int. Cl. H01j 7/16 US. Cl. 313--7 3 Claims ABSTRACT OF THE DISCLOSURE A vacuum gage having an anode defining an ionization chamber adapted for containing a fluid whose pressure is to be measured, a cathode being adjacent the anode for emitting electrons to ionize the fluid in the chamber such that the ions flow through an orifice in the chamber to a collector located outside the chamber and adjacent the orifice, the ion flow to the collector being a function of the fluid pressure in the chamber.

Brief summary of the invention The invention relates to an ionization vacuum gage (operating without magnetic field) for the measurement of low pressures of such a low range that difficulties are normally encountered in such measurements. According to the invention the gage is constructed to effect separation of the ionic current serving for the measure of pressure from spurious currents which, together with the ionic current, ordinarily reach the ion collector.

One of the currents which mainly disturbs the measurement is the current resulting from the emission of electrons by the collector under the influence of electromagnetic rays acting on the collector; these are mainly X-rays from the anode, as Well as ultraviolet light from the heated cathode.

To reduce these disadvantageous eifects, the gages known so far are characterized by the following construction:

(a) the collector has reduced dimensions (b) means is provided for the interception of electrons emitted by the collector (c) the collector is screened against undesirable radiation (d) the collector is located apart from the radiation source (e) means is provided for modulation of the ionic current.

These ionization vacuum gages have many deficiencies among which are, for example, low sensitivity, a complicated system of electrodes making thorough degassing diflicult, and complicated measurement techniques, etc.

The collector of reduced dimensions used in the vacuum gage of the invention may be screened and placed apart from the radiation source. Furthermore, the collector is located so that, even without screening, the effect of X-rays from the anode is considerably reduced, and the ultraviolet light from the cathode does not reach the collector at all, while the ions, which are a measure of the pressure, flow to the collector.

In order to increase the sensitivity of the vacuum gage, the ion collector is surrounded by a glass screen preventing dispersion of the ions flowing toward the collector while the screen also prevents the influx of ions from behind the anode and protects the collector against electrical disturbances.

3,463,956 Patented Aug. 26, 1969 ice Brief description of the drawing Detailed description In FIG. 1 there is shown a gage having an anode comstituted by a cylinder 1 of wire grid material with end covers 2, 3. The cylinder 1 and the covers 2, 3 define an ionization chamber in which the gas whose pressure is to be measured is ionized, as will be explained later. The cover 2 is also made of wire grid material. Cover 3 is similarly made of grid material, although it can be made of solid metal plate, as shown at 3' in FIG. 4. The cover 3 or 3' is formed with a central orifice 4. A cathode 5 is located adjacent the ionization chamber and acts to emit electrons to elfect a gas ionization within the chamber.

The anode is subjected to a positive potential causing electrons, emitted from the cathode, to be accelerated in the direction of the anode, to pass through the open spaces of the grid material and oscillate within the chamber until the energy of the electrons is spent by contact thereof with the solid material of the grid material. The gas within the chamber is ionized, the concentration of ions produced being a function of the gas pressure. These ions flow in the form of a current through the orifice 4 to a collector 6, which is at a potential lower than that of the anode. The collector 6 is in the form of a thin rod as shown in FIGS. 1-4 and located outside the ionization chamber and adjacent the orifice. The ionic current flow in the collector 6 is a measure of the gas pressure in the chamber.

A cylinder 7 surrounds the collector 6 and serves to prevent ion dispersion While protecting the collector 6 from the flow of ions laterally towards the collector. The cylinder also serves to protect the collector against disturbances caused by external electrical fields. The cylinder may be made of a metal plate 7, as shown in FIGS. 1 and 3.

The cylinder may also be formed, as shown at 8 in FIG. 2, integrally with the glass walls 9 of the enclosure for the chamber, anode, cathode and collector. Alternatively, the chamber may be constituted of grid material, as shown at 7' in FIG. 3, in which case a solid metal plate 10 is used.

The cylinder prevents dispersion of the ions as they flow to the collector and it protects the collector against the lateral influx of ions flowing from behind the anode (for example, from the surface of walls 9) as well as against disturbances from external electric fields.

Due to the location of the collector 6 outside the chamber and adjacent the orifice 4, the efiect of X-rays from the anode on the collector is considerably reduced. The cover 3' of solid material (FIG. 4)- and the plate 10 (FIG. 3) are effective to intercept radiation from the cathode 5 and prevent it from irradiating the collector. The plate 10 can also be used as a modulator in the modulation method of vacuum measurement.

To enable heating of the cylinder 7 in the process of electronic degassing, the collector 6 can be formed with a pointed end as shown at 11 in FIG. 4, so that when the collector 6 is heated, it acts as a cathode to produce electron emission.

For further reduction of the X-ray eflfect on the collector from the end cover, an additional screen 12 (FIG. 4) is placed between the end cover and the collector to block the X-rays while allowing the ions to reach the collector. This additional screen 12 can be used as a modulator in the modulation method of vacuum measurement by application of controlled voltage thereto.

What is claimed is:

1. An ionization vacuum gage for ultra-low pressures comprising means defining an enclosure, ionization electrode means in said enclosure including an anode chamher constituted by a perforated body with an outlet orifice, and a cathode adjacent said anode chamber, and an ion collector outside said ion chamber adjacent said outlet orifice, said collector comprising a thin rod facing said outlet orifice, and a glass cylinder encircling said rod.

2. A gage as claimed in claim 1 wherein said enclosure has glass walls and said glass cylinder is integrally formed with the glass Walls.

3. A gage as claimed in claim 1 wherein said rod extends parallel to the cathode, and perpendicular to the plane of the outlet orifice.

References Cited UNITED STATES PATENTS 10 JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner 

